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How to troubleshoot sendmail relay problem?

Posted on 1997-09-02
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Last Modified: 2013-12-23

I have two hpux boxes (box1 and box2) that have identical sendmail .cf files, and are set up to send all emails to box3 (as a relay host). Box2 works fine. It sends its mail to box3 and disconnects.

Box1 sendmail however, sends its email to box3 and then waits till box3 passes the email to the remote email host box.

Like I said the .cf files look identical. How do I troubleshoot this? I used sendmail verbose mode to verify the above situation. What would you look for?

                           Thanks for your help!
                           Keith Kwiatek
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Question by:keithedward
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4 Comments
 

Expert Comment

by:sisyphus
ID: 1582393
The first thing to do is a simple "diff" on the two files.  If they do, in fact, turn out to be identical, then check the following options:

# "Smart" relay host (may be null)
DS
# This should be set to box3

# default delivery mode
O DeliveryMode=background

# open connection cache size
O ConnectionCacheSize=2

# open connection cache timeout
O ConnectionCacheTimeout=5m
# Make sure it is set to a low setting since you are doing relaying.

Also, make sure you are using the latest version of sendmail (8.8.7) available at ftp.sendmail.org.

Hope this helps.

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Expert Comment

by:sisyphus
ID: 1582394
One more thing.  Make sure both box1 and box2 have an entry for box3 in the /etc/hosts files.  This should help to avoid unneeded DNS lookups.  
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Author Comment

by:keithedward
ID: 1582395
I am sure they are identical. I have check all the settings. I can take the .cf file from the "bad" box (which won't disconnect from the relay box until the relay box has sent the message to the remote host) and put it on the other "good" box and sendmail works fine (it connects to the relay host, sends the message and disconnects)....which is leading me to think it is not a sendmail .cf problem, but some other aspect of sendmail or maybe unix networks....
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Accepted Solution

by:
jantypas earned 200 total points
ID: 1582396
Good morning,

You've probably already tried this, but, in general, to debug sendmail files, one gets very cozy with the -d switch.  Depending on the age of your sendmail, you may regret it.  Older sendmail debug output resembles (correctly) line noise (^P^Q$R etc.).  However, we'll assume you have young sendmail and the debug output is from this planet.

- Invoke your machines sendmail manually with something
  like /usr/lib/sendmail -v -d21.99 <address>.  The -d#
  flag sets sendmail up in "super debugging mode".  Some
  sendmails go even higher -- you will get PAGES out debug outp
  output.

  Each stanza or rule as its output is decoded in front
  of you.  Without seeing your cf files, I can't say what
  your rulesets are doing, but pay close attention to your
  rulesets 3, 6, and 0.  In my world (Sendmail 8.8.x),
  these handle the preprocessing, name cracking and final
  delivery of SENT messages.

  To test a ruleset manually, use the -bt option such as:

    /usr/lib/sendmail -bt -d21.99 <foo@bar>

  Once in test mode (-bt), you can then individually
  test rules (such as S6) by typing something like:

  > 6 foo@bar

  to see how the address is cracked from rule 6 and beyond.

  NOTE: Some rules, particularly those that aid in anti-spam
        measures such as check_relay (a) are not named
        numerically (but will show up in debug as rull 998
        or some other odd number) (b) do not run until
        message delivery and (c) expect you to put in
        all the special operator tokens ($|) during
        debug.

You probably already have this on your shelf, but in
case you don't, go get the O'Relly book "Sendmail".
A classic O&A book, big, thick, loaded with detail,
but essential for sendmail cracking.

Lastly, this sounds like a cop out- but I've found most
networks need sendmail at the hub -- too many things go
on there, but most *interior* nodes, use a tenth of
sendmail's abilities.  I've replaced sendmail on interior nodes
with something that's easier to maintain such as qMail or
smail.  They're not as powerful as sendmail, but your admins will
thank you for it.

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